Light emitting diodes (LEDs) are an efficient source of light. By utilizing a plurality of LEDs in a defined arrangement, the LEDs may be utilized to provide an alternative to current luminaires, such as incandescent bulbs and fluorescent tubes. In order for LED luminaires (e.g., bulbs, tubes, fixtures) to be widely adapted they need to be able to replace current luminaires (e.g., incandescent bulbs, fluorescent tubes) in existing lighting configurations (e.g., troffers).
FIG. 1 illustrates a high level functional diagram of an example troffer 100 commonly used to provide fluorescent lighting in commercial establishments (e.g., office buildings, retail stores, apartment complexes, hotels). The troffer 100 includes a housing (not separately identified in the figure) that is typically located in the ceiling and houses a plurality of fluorescent tubes 110 (four illustrated). The troffer 100 includes clips 120 that are utilized to hold the fluorescent tubes 110 and to provide the appropriate power thereto. The tubes 110 need a high initial voltage to begin operation (lighting) and then require a regulated current to operate. Accordingly, the troffer 100 includes a ballast 130 that receives the line power (e.g., 120V, 240V) 190 for the establishment and provides an initial striking voltage to the tubes 110 to initiate operation and then maintains a regulated current to the tubes 110. The troffer 110 includes wires incorporated therein (not illustrated) that connect the ballast 130 to the clips 120.
As illustrated, the ballast 130 is a single device connected to the plurality of fluorescent tubes 110 but is not limited thereto. Rather, multiple ballasts could be utilized with each ballast providing power to one or more fluorescent tubes 110.
A retrofitted LED tube needs to have the same, substantially the same, or similar footprint and form factor (hereinafter, for ease, simply referred to as same footprint) to be able to replace the florescent tube 110 in the troffer 100. However, the power requirements for an LED tube are different than the power requirements for florescent tubes 110. The ballast 130 used with florescent tubes 110 is not capable of providing the power requirements of the LED tubes and is typically removed, disconnected, or deactivated (simply referred to hereinafter as removed for convenience) in retrofits. A power supply/driver is required to convert the line power 190 to the appropriate power requirements of the LED tubes.
Often retrofit LED tubes use individualized power supplies built into each tube and each tube is directly connected to the line power 190. This may require the removal of the ballast 130 from the troffer 100. The LED tubes may be connected to the line power 190 via the clips 120 if, for example, the troffer 100 is modified so the wires incorporated therein that typically are used to connect the clips 120 to the ballast 130 are disconnected from the ballast 130 and are connected directly to the line power 190. Alternatively, the LED tubes may include connectors and/or wires extending therefrom for connecting directly to the line power 190.
Requiring the ballast 130 to be removed and connecting the line power 190 directly to the LED tubes adds to the labor costs of retrofitting the light troffers 100 with LED tubes. This operation may require skilled professionals (e.g., electricians) and may pose a safety hazard as contact with the line power 190 may occur. Furthermore having the line power 190 on the clips 120 may propose a hazard when the LED tubes are replaced as an installer may inadvertently contact the line power 190.
Moreover, encapsulating a power supply within a tube generates additional unnecessary heat that is trapped therewithin. This additional heat adversely affects the LEDs themselves, altering color temperature and shortening their expected lifespan. Moreover, the power supply may have a life span less then that of the LEDs and thus be the limiting factor in the life of the LED tubes.
FIG. 2 illustrates a cross sectional view of an example LED tube 200 commonly used as a replacement for fluorescent tubes. The tube 200 includes an extrusion 210, a lens 220, a circuit board 230 having LEDs 240 mounted thereon, and a power supply 250. The extrusion 210 is made of aluminum so that it may act as a heat sink for the board 230. The extrusion 210 is substantially semicircular so as to provide a bottom portion (approximately ½) of the body of the tube 200. The extrusion 210 may include a ledge, groove 214 formed in an inner surface and the board 230 may rest and be secured therewithin. The board 230 thus is located at approximately the middle of the tube 200 so that the power supply 250 can be located therebelow in the lower half of the tube 200. As the ledge 214 only provides support for the edges of the board 230, the board 230 is in effect floating in the middle of the tube 200. Because the extrusion 210 only contacts the outer edges of the board 230 at the ledge 214 the heat dissipated from the board 230 is limited (the extrusion 210 provides limited thermal management).
The lens 220 is substantially semicircular so as to provide a top portion (approximately ½) of the body of the tube 200. The extrusion 210 and the lens 220 connect together to form the outer body of the tube 200. The extrusion 210 may have a slot or grove 212 formed in an outer surface for receiving the lens 220, for example, a lip (not separately illustrated) formed in an outer edge of the lens 220. The lens 220 is acrylic or plastic.
The LEDs 240 on the board 230 may emit light in one direction, down and out at approximately 120 degrees. While this maximizes the LED light output, the result is that LED tubes provide light much more directionally then fluorescent tubes 110. The use of the extrusion 210 as part of the outer body of the tube 200 further limits how the light will be dispersed as no light will be able to exit therefrom. That is, any light, even light reflecting within the tube 200, is limited to exiting the lens 220 (approximately 180 degrees). Furthermore, the extrusion 210 prevents uplighting within the troffer (light illuminating the top of the troffer and/or reflecting therefrom). The result of the directional light provided by the LEDs 240 and the limited dispersion of light from the tube 200 may provide a reflective interior of the troffer that appears “dim”, which not only creates an aesthetic distraction, but reduces lumen output.
FIG. 3 illustrates a high level functional diagram of an example troffer 100 commonly used when retrofitting example LED tubes 200 having individualized power supplies 250 therewithin. The ballast was removed and the line power 190 is connected directly the clips 120, the wires incorporated in the troffer 100 that typically connect the clips 120 to the ballast are instead connected directly to the line power 190.